Differential microphone-transmitter.



J. J. comm, DIFFERENTIAL MICROPHONE TRANSMITTER.

APPLIOATIONIILED OUT. 24, 1910. v

Patented July 23, 1912.

s sums-S33E11.

Y J .'J. GOMER. I DIFFERENTIAL MICROPHONE TRANSMITTER.

1 urmmm'ox mum 001,24, 1910.

atented July 23,1912:

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WI /E5553 Jenn J. comes, on CHICAGO, ILLINOIS, Assrenon'roAUTOMATIC-ENUNCIATORW:

COMPANY, OI! CHICAGO, ILLINOIS, A CORPORATION OF ILLINOI DIFFERENTIALMIcnorHonE-TRAnsMrrTER. r

Specification of Letters Patent.

perennially 23, 1912.

Application filed October 24, 1510. Serial at. 588,788.

To all whom it may concern? Be it known that I ,'JO IIN J; COMER, "acitizen of the United States of America, andresident of Chicago,Cookcounty, 'Illinois, 'haveanvented a certain .new and usefulIn'iprovement in Differential 'Microphone- .lransmitters, of which thefollowing is a specification.

My invention relates to transmitters of the kind ordinarily knownasdilferential transmitters. Theobject of my invention is to provide animproved construction and arrangement whereby the plunger orintermediate electrode 'ofa transinitterof this kind is heldstationarybetween two movable electrodes.

[In this wayI combine the agit ation'or shaking of. the carbon granuleswith the differ-1 ential principle of transmission in' a microphone inwhich at least one of the electrodes is stationary. Such atransmitteris, I find, especially adapted for use in loud speaking systems, or insystems forloud transmission,

such, forexample, as those employed for music or other similar purposes,it being es sential in such cases that the enunciation and tone be clearand. pure, and it being necessary very often, in order to obtain theseresults, to use heavy currents, or: at least currents much =tooheavy forthe ordinary showing another form of my invention.-

Figs. 7, 8 and 9 are similar views showing still a thirdform of myinvention;

As'thus illustrated, and referring to Figs. 1 to 3 inclusive, thetransmitter comprises the front plate A having an opening therein fortheusual mouthpiece B. I The 'diae phragm O is seated against ashoulder aon the inside of said" plate, and'insulated,

therefrom, as shown, and heldin place by a disk D which is in electricalcontact therewit'h. Said disk is provided with a central aperture (Z andis, held in place by a clampand is, ther ing rin'g E, that screws intosaid plate A,

and disk whereby the diaphragm and disk are insulated from the plate A,in themam ner shown. A' sheet metal boxorcu ,I! has its mouthoropenendprovided with there being insulation between the said ring aflange fwhich is secured to the b'ack of the diaphragm C, todorin aamicrophoriechamber for containing the'front and back electrodes f and f and. thegranular carbon f- The sald -fro'nt electrode is'secured byla l1ollowrivet-f* to the diaplira'gnniand the Stud back electrode is secured-by ahollow The granular carbon f is insulated from the box F by acylinder ofmica "The fined or stat onary electrode f 'i's secured'toa stem] f andinterposed between thetwdmovable' electrodes,-bcing in the nature of aplunger. Th s stem-extends v tl1 ro'u, 3;h the rivet f and 4 1sadjustably secured to the bridge f, which rivet f to the back wallfi ofthebox F, be-

' ing separated therefrom by a disk of mica f I latter-is secured to thedisk D but insulated I therefrom. Fluffy asbestos is used for fill,- mgthe holes i-n the rivets ffand 'f, to pre-' ve'nt the granular carbonfrom escaping, the

opening in the rivet f being used for filling the box-that 1s, fornitrodu'cmg the -.said

granular carbon after the parts are all as sembled. The circuits forsaid electrodes I may be of any suitable cl'iaracter. As shown, oneterminal wiregoes-to the disk D, to thereby in etfe'ctconnect with thefront electrode f another' oes to the screw that is secured to the backelectrode f and the third'wire-connectswith the bridge f tovtherebyconnect with the electrode fh' 'lVhen operated differentially, Ijfi'ndthat the .above described microphone transmitter will producegoodresults with heavy currents,

in loud-speaking. systems.

efore, especially adapted for:use

In'Figs. -ft to 6 inclusive, the construction I substantially the sameas that previously described, except that in this case the microphonebox' or cup G -.has the integral end wall g thereof secured to-thediaphragm,

and-the open rear end of said box or cup 15- closed by a cap 9 offlexible sheet metal.

i In Figs. 7 to 9, inclusive,'the construction is in effect the same asthat shown in Figs. I 1 to.3,'except that the microphone box 11 isdisposed in an opening in the center of the diaphragm, and is.formed bytwo cups or. halves it and it that are secured to opposite sides of thediaphragm to cover said opening'and form a chamber between them, Thusit- Will be seen that I provide -a microphone box that 1s secured to thed12- -pl1r2\gm, and that-t-l e mode of operation isv such that the saidbox, althoughpreferably made of sheet metal. does not need aflexiblewall or auxiliary diaphragm, both" the front and back electrodesmove byreason of the flexibility of the single lE -rge' and usual diaphragm.while the middle or intermediate electrode remains fixed. or.statioriarj to increase tl e resistance first on one side-thereof andthen on the other.

What I claim as my invention is:

1. In a transinitterya diaphragm, "front and back electrodes carried byand movable w th saiddmpliragm, a stationary electrode between saidfrontand back el'ectrmles, a support, :and a connection, from said sin--tionaryelectrode to said'snpport l 'WlllCll con- I nection is securedtojsaid support.-

2. 111 a transmitter, a diaphragm, a' support, a differentialmicrophonebox carried on-sziid 'diaplirag ire icl movable therewith, a connectionextending lIlSldQ of said box,

and .meansbfor securing said connectionto said support.

3. in a transmit-tenedizrpliragm, a diiy ferential microphpnebox mountedon and momblewith said diaphragm, adisk for clamping said diaphragm inplace a bridge on said disk, and a connection-secured 'to sdid bridgeand extending inside of said extending through one of said movableelectrodes to saidstationary electrode o. In a transmitter, avdiaplimgm, a" difiierential microphone lion mounted on and movable withsaid d aphragm, asnpport, a

connection extending inside of said micro phone, and .means foradpistably securing said connection; to said support;

- Signed ,b v me at t liicago, Illinois, this 12th day of October; 1910.v

JOHN J."CO1\'IER. W it-nesses he B. DURNION, ,E. H. CLEGG..

